Propeller control mechanism



NOV. 17, 1942. -rm 2,302,042

PROPELLER CONTROL MECHANISM Filed Dec. 18, 1937 2 Sheets-Sheet 1INVENTOR. E119 Marlin A TTORNEY Nov. 17, 1942. I E, MAR' N I 2,302,042

PROPELLER CONTROL MECHANISM Filed Dec; 18, 1937' 1 2 Sheets-Sheet 2 My aINVENTOR. Erl Marlin A TTORNE Y Patented Nov. 1 7, 1942 PROPELLERCONTROL IMECHANISM Eric Martin, West Hartford, Conn, assignor to UnitedAircraft Corporation, East Hartford, Conn.,' a corporation of DelawareApplication December 18,1937, Serial No. 180,592 7 Claims. (01.I'm-135.6)

This invention relates to improvements in control means for controllablepitch propellers and has for an object the provision of an improvedcontrol means for regulating the propeller speed and for maintaining twoor more pfopellers in synchronism with each other automatically whilemaking provision for a manual control whenever desired.

Other objects and advantages will be more particularly pointed outhereinafter or will become apparent as the description proceeds.

In the accompanying drawings in which like reference numerals are usedto designate similar parts throughout, there is schematicallyillustrated a combination of elements arranged according to what is nowconsidered'to be the preferred form 01' the invention, and a somewhatmodified arrangement of similar elements. The

drawings. however, are for the purpose of illustration only and are notto be taken as in any way limiting the scope of the invention.

In the drawings,

Fig. 1. is a schematic illustration showing two engines and controllablepitch propellers driven thereby, and electrically actuated devices forregulating the speed of the propellers and maintaining the propellers insynchronization with each other and,

Fig. 2 is a schematic illustration of an arrangement wherein two or morepropellers are driven by the same engine and the thrust of the twopropellers is equalized by suitable electrically actuated devices.

Referring to the drawings in detail and particularly to Fig. l, the twoengines, schematically illustrated, are indicated by the referencenumera-ls Ill and I2 and the controllable pitch propellers driven by theengines are generally indicated by the numerals l4 and I6 respectively.While only two engines and two engine-driven propellers have beenillustrated,iit is to be understood that the application of theinvention is not limited to any particular number of engines orpropellers.

The controllable pitch propellers l4 and I8 may be of the featheringtype, having rotatably mounted blades l8 provided with beveled gearsectors which mesh. with a pitch changing gear 20 rotated by poweractuated means under suitable manual or automatic control. Thisinvention contemplates changing the pitch oi the propeller blades byactuating the pitch changing mechanism by an electro-magnetic motordevice comprising a wound field and a wound armature separately excited,which device will be herein- 5 after referred to as a "Selsyn" unit.Each Selsyn. unit has a relatively rotatable part or rotor 22 and arelatively stationary part or stator 24. For convenience in theexplanation the Selsyn unit connected with the propeller I4 is generallydesignated by the numeral 28 and the Selsyn unit connected with thepropeller I6 is generally designated by the numeral 28. I

Between the rotor 22 of each Selsyn and the pitch'changing gear 20 thereis provided a suitable'reduction gear unit 30 having a reduction factorof the order of several thousand to one. The Selsyn ispreferably mountedon or in the forward portion of the propeller hub and is directlyconnected to the propeller blades through the reduction gear 30 and thepitch changing gear 20 and the blade carried gear sectors.

The propeller speed is regulated by some suit able form of constantspeed device which may be a governor controlled engine but which, forthe sake of convenience, has been shown as a constant speed electricmotor connected with some suitable source of energy such as the battery34 and provided with a manually actuatable speed controlling device suchas the rheostat 36. This motor drives a three-phase alternating currentv generator, generally indicated by the numeral 38, which includes arotor portion 40 and a stator or field portion 42. The stator portion 42of the alternator 38 is connected in parallel by means of suitableelectrical conduits and three of thesix collector rings, generallyindicated at 44, with the stator 24 of the Selsyn 2B and is similarlyconnected by means or three of thesix collector rings, generallyindicated at 46, with the stator portion of the Selsyn unit generallyindicated at 28.

Each of the engines drives a three-phase alternator, the one driven bythe engine It being generally indicated at 48, and comprising a rotorportion and a field or stator portion 52-, while the alternator drivenby the engine i2 is generally indicated at 54 and comprises a rotorportion 56 and a field or stator portion 58. The

stator of the generator or alternator 48 is connected to the rotor 22 ofthe Selsyn unit, generally indicated at 26. by means of suitableelectrical conduits, and the three of the six collector rings 44 notused to connect the stator 42 with the stator 24. The stator 58 of thealternator 54 is similarly connected to the rotor of the Selsyn unit 28by means of suitable electrical conduits and the corresponding three ofthe six collector rings generally indicated at 46. The collector rings44 and 44 are preferably mounted upon the propellor drive shaft betweenthe propeller and the adjacent portion of the engine and are contactedby fixed brushes carried by the adjacent portion of the engine. They arepreferably concentric and arranged in side by side relation with respectto each other and separated by suitable insulating materials. The ringsand brushes and brush holders may be encased in an engine carried covermember in a manner well-known to the art.

With the above described arrangement the stators or field portions ofthe two Selsyn units 28 and 28 will be energized by the three-phaseelectrical impulses from the alternating current generator 38 driven bythe controllable constant speed motor 32. The rotor portion of theSelsyn unit 28 will be energized by the three-phase alternating currentimpulses from the alternating current generator 48 driven by the enginel8 and the rotor portion of the Selsyn unit 28 will be energized by thethree-phase alternating current impulses delivered by the alternatingcurrent generator 54 driven by the engine I2. If either one of theengines I8 or I2 tends to get out of synchronism with the constant speedmotor 82, there will be a difference in the frequency and a change inthe phase relation of the alternating current impulses energizing thestator and rotor portions of the Selsyn unit carried by the propellerdriven by that engine, which frequency difference and consequent phaserelation change will cause the rotor portion of the Selsyn unit torotate relative to the stator portion of the unit thereby operating thepropeller pitch adjusting mechanism to change the pitch of the blades ofthe respective propeller. This change in propeller pitch will alter theload on the engine and cause it to return to a condition of synchronismwith the constant speed motor.

The speed of the constant speed motor 82 may be controlled bymanipulation of the variable resistant rheostat 38 so that the twoengines may be regulated to operate in synchronism with each other atany desired speed within the range of the apparatus.

In case a governed engine is used as the master speed control instead ofthe constant speed electric motor 32, the speed may be manuallycontrolled by changing the setting of the governor on the governedengine.

At various times it may be desirable to place the propellersindividually under manual control to change the pitch setting thereof orto bring the propeller blades into or out of a feathered condition. Inthe arrangement illustrated this may be accomplished by means ofsuitable manually operable switches located in convenient reach of theoperator of the vehicle upon which the engines and propellers aremounted. The manually operable switches generally indicated at 88 and82, are provided for the control of the propeller I4 while the similarswitches, generally indicated at 84 and 88, are provided for the controlof the propeller IS.

The switch ,88 is a double throw switch disposed in the circuit leadingfrom the stator 52 to t1 e rotor 22 of the Selsyn unit 28 and has twoopera tive positions in the first of which, as illustrated, it directlyconnects the individual windings of the stator 52 with the correspondingindividual windings of the rotor 22, and in the other of which itdisconnects the stator 52 from the rotor 22 and short-circuits some ofthe windings of the rotor 22 to convert the Selsyn unit 26 into aninduction motor in a manner well-known to the art.

The manually operable switch 62 is a double throw switch disposed in thethree electrical conduits connecting the individual windings of thestator 42 with the corresponding windings of the stator 24 and isoperative to reverse the connection between the individual windings ofthe stator 42 and the individual windings of the stator 24 so that theinduction motor, provided by shortcircuiting some of the windings of therotor 22, may be caused to rotate in either direction to move the bladesof the corresponding propeller I4 toward either a high-pitch or alow-pitch position. In this manually controlled pitch changing operationthe generator 38 furnishes the power for operating the induction motorprovided by short-circuiting some of the windings of the rotor of theSelsyn unit 28 and this power is transmitted through the reduction gear38 to the pitch changing mechanism of the propeller.

The switches 64 and 66 operate in the same manner with relation to theSelsyn unit 28 and propeller I6 as the corresponding switches 88 and 82operate in connection with the Selsyn unit 28 and propeller I4 asexplained above, and the generator 38 also furnishes the power foroperating the unit 28 as a motor.

In the modified form of the invention illus trated in Fig. 2, the engine88 drives a plurality of propellers, as generally indicated at I8 andI2, through suitable gearings generally indicated at I4.

In this case it will be obvious that the two propellers I8 and I2 willalways rotate in synchronism with each other by reason of theinterconnection between them through the gearing I4, and the conditionto be maintained is an equalization of the thrusts developed by the twopropellers. Each of the propellers I8 and I2 is a controllable pitchpropeller incorporating pitch adjusting mechanism of a suitable formsuch as the intermeshing gear elements, generally indicated at I8 and18, respectively, driven through respective reduction gears 88 and 82 byrespective propeller carried Selsyn units, generally indicated at 84 and88. The Selsyn unit 84 comprises a rotor portion 88 and a stator portion88 and the unit 88 comprises a similar rotor portion 82 and statorportion 84. The two rotor portions 88 and 82 are connected, preferablythrough suitable slip rings, such as are indicated in Fig. 1, with thethree phase wound stator 88 of an alternating current generator,generally indicated at 88, having a rotor portion I88, driven by theengine 88. The stator portions 88 and 84 of the Selsyn units 84 and 88,are connected, also preferably through suitable slip ring and brushconnections, with the three phase wound stator I82 of an alternatingcurrent generator, generally indicated at I84, hav-' ing a rotor portionI88 driven by a constant speed motor I88 energized from a suitablesource of energy such as the battery I I8 and manually controlled as tospeed range by an adjustable rheostat H2.

With this arrangement, if the motor 88 gets out of synchronism with themaster control I88 2. frequency difference will be created between thealternating current of generator I84 driven by the master control andthe alternating current of generator 88 driven by the engine. Since thegenerators I84 and 88 are connected respectively to the stators 98 and84 and the rotors 88 and 82 of the Selsyn units 84 and 86, thisdifference in frequency between the alternating currents ofsimultaneously adjust the pitch of the two pro-' pellers to maintain thspeed of the engine in synchronism with the speed of the master controlwhile at the same time maintaining the pitch of the propellers the sameso that the thrust developed by the two propellers will be equalized. Itis to be understood, of course, that the same condition would applyregardless of the number of propellers driven by the engine. Provisionsfor manually controlling th propellers, similar to those described inconnection with Fig. 1 may be made if desired.

While there has been schematically illustrated and briefly described twopossible combinations of elements arranged according to the invention,it is to be understood that the invention is in no way limited to thearrangement so illustrated and described but that such changes thereinmay be resorted to as come within the scope of the sub- Joined claims.

Havingnow described the invention so that others skilled in the art mayclearly understand the same, what it is desired to secure by LettersPatent is as follows:

1. Speed control and. synchronizing means for h a plurality ofcontrollable pitch propellers comprising respective electric units, eachunit comprising an alternating current motor device hav- "ing separaterelatively rotatable field and rotor portions, said rotor portion havinga direct mechanical connection to the blades of the respective propellerfor directly changing the pitch thereof, respectivealternating currentgenerating devices each driven at a speed proportional to the speed ofits respective propeller and electrically connected to one relativelyrotatable portion of the corresponding electrical unit, and alternatingcurrent generating means driven at a controlled speed electricallyconnected in parallel to the alternativ relatively rotatable portions ofall of said units.

2. In a control means for controllable pitchv propellers, an electricalunit comprising relatively gear carried by said propeller, said unitconstituting the sole source of power for moving the blades in at leastone direction to change their pitch, a master speed control, analternating current generator driven by said master control andelectrically connected with corresponding portions of all of said units,and individual alternating current generators driven respectively by theseveral propeller driving means and electrically connected to the otherportion of each respective unit to render said units operative to changethe pitch of the respective propellers whenever there is a frequencydifference in the outputs of the generators connected respectivelythereto, the output of each of said individual generators being at thesame frequency as the output of said master control driven generator aslong as the speed of the respective propeller is in synchronism with thespeed of said master control.

4. In a thrust equalizing control for a plurality of coactingcontrollable pitch propellers having a common driving means, an electricmotor unit comprising relatively rotatable separately excited portionscarried by each of said propellers and having the rotor portion thereofmechanically connected with the pitch changing mechanism of therespective propeller a master speed control, analternating currentgenerator driven 1 en by said common propeller drive and electricallyconnected in parallel to the rotor portions of all of said units.

5. Speed control and synchronizing means for a group of controllablpitch propellers each having a hub and a plurality of blades rotatablymounted in said hub comprising, an electric motor device for each hub,each motor device having a wound stator element carried by therespective hub and a wound rotor element operatively connected with therespective hub supported blades, an alternating current generator foreach rotatable portions carried by a propeller and connected with thepropeller pitch changing mechanism solely by reduction gearing carriedby said propeller, said portions being relatively moved by the eiIectsof alternating current applied thereto,

and'constituting the sole source of power for moving the blades in atleast one direction to change their pitch, a master speed control, meansdriven by said master speed control for applying a multi-phasealternating current to one relatively rotatable part of said unit, andmeans driven by the propeller driving means for applying a multi-phasealternating current to the ther relatively rotatable part of said unit,said two means being timed with respect to each other so that the twocurrents have the same frequency as long as said propeller is driven ata speed in synchronism with the speed of said master control.

3. In a speed and synchronizing control for a plurality of coactingcontrollable pitch propellers, an -electric motor speed comparing andpitch changing unit carried by each propeller and operatively connectedwith the respective propeller propeller driven at a speed having a fixedrelation to the speed oi. the respective propeller and connected to oneelement of the respective motor device, and an alternating currentgenerator driven at a reference speed and electricallyconnected inparallel to the other elements of all of said motor devices andrespective manually operable switch means electrically'connected withits respective electric motor device and one of its energizinggenerators operative to convert said electric motor device between acondition in which it operates in response to a frequency difference inthe two alternating currents supplied thereto and a condition in whichit operates as a motor energized by a single supply of alternatingcurrent by varying the internal circuit of said unit and the, connectionbetween said unit and the generator connected with said switch, andelectric control means for controlling the operation of said unit whenacting as a motor energized by a single supply of alternating current.

6. In combination, an engine driven controllable pitch propeller, analternating current electric generator and means for driving the samefor establishing a reference speed, an alternating current electricgenerator driven at a speed bearing a fixed relation to the speed ofsaid propeller, and electrically operated means mounted to rotate withand operatively associated with said propeller and having a portionthereof directly mechanically connected with the blades of saidpropeller, and means electrically connecting said electrically operatedmeans with both of said generators to supply the energy for changing thepitch of said propellers and to convert a frequency difference in theelectrical output of said generators into a pitch change of saidpropeller to maintain said propeller speed in synchronism with saidreference speed.

7. In combination with a controllable pitch propeller, an electricallyactuated speed comparing unit carried by said propeller and mechanicallyconnected with the propeller blades, for changing the pitch thereof,said unit supplying all the energy for changing the blade pitch in atleast one direction, said unit having separately energized field androtor portions relatively rotatable in response to a frequencydifference in the alternating current supplied respectively thereto, agenerator driven at a reference speed electrically connected with onepart of said speed comparing unit, an alternating current generatordriven at a speed proportional to the speed of said propellerelectrically connected to the other portion of said speed comparingunit, and manually operable switch means electrically connected withsaid speed comparing unit and one of said generators operative toconvert said speed comparing unit, between a condition in which itoperates in response to a frequency difl'erence in the two alternatingcurrents supplied thereto and a condition in which it operates as amotor energized by a single supply of alternatin current, by varying theinternal circuits of said unit and the connections between said unit andsaid generators, and a switch for controlling the operation of said unitwhen acting as a motor energized by one of said generators.

ERLE MARTIN.

